Add setAllowedAuthenticators(int) to BiometricPrompt

Introduces a BiometricPrompt.PromptInfo#setAllowedAuthenticators(int)
method to allow a caller to specify whether to allow BiometricPrompt to
authenticate with device credential, biometric auth, or either. Also
renames the non-public Authenticator class to Authenticators, to avoid a
name collision and potential confusion with other Authenticator classes.

Test: make -j update-api
Test: atest AuthBiometricViewTest
Test: atest AuthContainerViewTest
Test: atest AuthControllerTest
Test: atest BiometricServiceTest

Bug: 80525177
Change-Id: I51da3ff0dcc7e49adb2d7f1c9cdaa12a55b11565